Implement the editor in pure Qt

> Rewriting the editor in pure Qt will achieve the following:
>
> * Easy to implement. Can be done in less than 1000 lines.
> * Will work fast unlike the Electron-like experience we have today.
> * No web implementation. No need to pass messages between python and web.
> * mediasrv will not be needed.
> * no race conditions since everything is handled by qt.
> * the mentioned *in-Svelte browse screen* isn't needed.

_Originally posted by @tatsumoto-ren in [#3830](https://github.com/ankitects/anki/issues/3830#issuecomment-3006354480)_